1. Field of the Invention
Exemplary aspects of the present invention generally relate to a liquid cooling type cooling device (liquid cooling device) using a liquid coolant and an image forming apparatus including the liquid cooling device.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, printers, facsimile machines, and multifunction devices having two or more of copying, printing, and facsimile capabilities, typically form an image of characters, symbols, or the like on a recording medium (e.g., a sheet of paper, an OHP sheet, etc.) according to image data using a variety of methods. Of these, an electrophotographic method that achieves higher definition images at higher speed is widely employed.
In the electrophotographic method, for example, an optical device reads image data of a document, a charger charges a surface of an image carrier (e.g., a photoconductor); a writing device emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a developing device develops the electrostatic latent image with a developer (e.g., toner) to form a toner image on the photoconductor; a transfer device transfers the toner image formed on the photoconductor onto a sheet of recording media; and a fixing device applies heat and pressure to the sheet bearing the toner image to fix the toner image onto the sheet. The sheet bearing the fixed toner image is then discharged from the image forming apparatus.
During image formation, driving of many devices provided within the image forming apparatus generate heat, and the heat thus generated increases the temperature within the image forming apparatus. For example, in the optical device, a scanner lamp that scans the document with light and a scanner motor that drives the scanner lamp both generate heat. In the writing device, a motor that rotates a polygon mirror at high speed generates heat. In the developing device, frictional heat is generated when toner is agitated to be charged, and in the fixing device, a heater that fixes the toner image onto the recording medium generates heat. In addition, in the case of duplex image formation, the recording medium heated by the fixing device passes through a conveyance path for duplex image formation, thereby increasing temperature around the conveyance path.
The heat thus generated causes various problems. For example, toner particles stored in the developing device can be melted together and coagulate, causing irregular images or a breakdown of the developing device when the melted toner is solidified, thereby locking moving parts within the developing device. The temperature increase within the image forming apparatus may further cause deterioration of oil applied to bearings and so forth, shorter mechanical life of a motor, malfunctions or breakdown of an IC on an electric substrate, and deformation of resin members with lower thermal resistance. To prevent the problems caused by the temperature increase within the image forming apparatuses, image forming apparatuses are typically provided with an air cooling type cooling device (air cooling device) that cools the interior of the apparatuses using cooling fans, ducts, and so forth.
However, the number of heat generators provided within the image forming apparatuses continues to increase along with faster processing speed. In addition, in order to meet demand for more compact image forming apparatuses, components tend to be densely packed within the apparatuses. Consequently, it is difficult to provide an optimal airflow system within the image forming apparatuses, thereby causing the heat to remain trapped in the interior of the image forming apparatuses. Further, toner having a lower melting point that reduces power consumption during fixing of the toner image onto the recording medium has been developed in order to meet increasing demand for energy saving. Therefore, a temperature increase within the image forming apparatuses needs to be more securely prevented particularly in a case of using such toner. For these reasons, it is difficult for the air cooling device to reliably cool the image forming apparatuses.
There is known a liquid cooling device that has a greater cooling capacity than that of the air cooling device. The liquid cooling device typically includes a heat receiving part disposed at a position where the temperature tends to increase in the image forming apparatus, a heat releasing part that releases heat from a liquid coolant, a circulation channel through which the liquid coolant circulates between the heat receiving part and the heat releasing part, a pump that causes the liquid coolant to flow through the circulation channel, and so forth. The liquid coolant is circulated between the heat receiving part and the heat releasing part by the pump so that the heat absorbed by the liquid coolant via the heat receiving part is released from the liquid coolant at the heat releasing part. Unlike the air cooling device, the liquid cooling device transports the heat using a liquid coolant which has a larger heat capacity than air. Therefore, the liquid cooling device has better heat receiving capability and can effectively cool the target.
However, at the same time, leakage of the liquid coolant within the image forming apparatus may occur. If the liquid coolant leaks from pipes or joints that couple the pipes of the circulation channel together and adheres to a power source or image forming units, not only irregular images but also a breakdown of the image forming apparatus may occur.
To solve the above-described problems, a related-art liquid cooling device 90 illustrated in FIG. 1 includes pipes 41 and 42 provided at input and output openings of a heat receiving part 310, respectively, a joint 45 that couples the pipe 41 to a tube 51, a joint 46 that couples the pipe 42 to a tube 52, and a pair of shielding members 80. The joints 45 and 46 are disposed within a space Z formed between the shielding members 80 and are isolated from an image forming unit including a developing device 400. Accordingly, in the event of leakage of the liquid coolant from the joints 45 and 46, the image forming units and so forth are prevented from getting wet with the liquid coolant.
The developing device, the fixing device, and so forth are often detachably installable in the image forming apparatus so that only the developing device or the fixing device need be replaced with a new device upon breakdown of the device or at the end of the service life of the device. In a case in which the developing device, for example, is detachably installable in the image forming apparatus, installation and detachment of the developing device to and from the image forming apparatus are facilitated by moving the heat receiving part to be separated from the developing device although the heat receiving part needs to contact the developing device so as to cool the developing device.
However, if the developing device 400 shown in FIG. 1 is detachably installable in the image forming apparatus, it is difficult to separate the heat receiving part 310 from the developing device 400 upon installation and detachment of the developing device 400. Specifically, the pipes 41 and 42 provided to the input and output openings of the heat receiving part 310, respectively, and the shielding members 80 prevent movement of the heat receiving part 310, thereby preventing separation of the heat receiving part 310 from the developing device 400. Thus, the related-art liquid cooling device is not suitable for cooling a developing device or other target that is detachably installable in the image forming apparatus.